The present invention relates to a device for reproducing a three-dimensional image with a background by use of an optical filter, which device can be used in the fields of image technology, broadcasting technology, the arts, the multimedia industry, cameras, and photographs.
Conventional techniques for recording and reproducing three-dimensional images are generally classified into two schemes; i.e., a scheme in which a three-dimensional image is recorded by some method, and the recorded image is reproduced for direct observation by an observer; and a stereoscope scheme in which, instead of a three-dimensional image, a two-dimensional image for the right eye and a two-dimensional image for the left eye are recorded, and the recorded images are reproduced such that an observer can see the image for the right eye through his right eye and the image for the left eye through his left eye.
Typical examples of the former are holograms and integral photography; and typical examples of the latter include three-dimensional movies to be observed by use of polarization glasses, and three-dimensional televisions utilizing a lenticular sheet.
In the latter case, although an image can be observed three-dimensionally, a three-dimensional image is not reproduced, and therefore that the image does not change even when the observation position is changed, and the back side of the image cannot be seen. Therefore, the latter scheme provides pseudo-production of three-dimensional images.
In holography, which is an ideal method of recording and reproducing three-dimensional images (hereinafter referred to as 3D images), data regarding the wave front of light emitted from an object are used in order to record three-dimensional image data. Wave front data are recorded in such a manner that scattered light from an object and separately provided reference light are caused to interfere with each other to thereby form interference fringes, and the thus-formed interference fringes are recorded. Therefore, an optical system and a recording medium to be used must have a spatial resolution close to the wavelength of light, and a coherent light source such as a laser must be used at least for recording. Since interference fringes depend on wavelength, handling of color images; i.e., recording of color images, requires three lasers, for the three primary colors, and a complex configuration.
Because of the above factors, full-color holography for large screen involves considerably high cost; therefore, holography is not used for real-time display of 3D images and three-dimensional movies, although holography is presently used for mediums for recording digital data, as well as for credit cards and ornaments, in which holography can be implemented in a small scale.
Integral photography is the same as a stereoscope in the point that a three-dimensional image is obtained by means of parallax. However, whereas a stereoscope is designed to enable a user to observe images of two angles of view through respective eyes and to attain solidity from binocular parallax, in the case of integral photography, an image is observed from many angles of view in order to record images of different view angles, and the images are reproduced simultaneously in order to provide an image which changes depending on viewing position.
Therefore, such integral photography has advantages in that an image changes upon movement of the eyes and that glasses are unnecessary. Moreover, integral photography has other many advantages, which cannot be attained by use of a holograph; e.g., recording and reproduction can be effected by use of ordinary light, and a background of infinite distance can be reproduced. However, in the case of integral photography, images of all angles of view are imaged at a certain position simultaneously (of course, only portions of the images can be observed from a specific direction). When a user focuses his/her eyes on that position, the user can see the images as being located at different positions. Therefore, the focus position does not coincide with a position of a viewed image, inevitably leading to the problem of unnaturalness (e.g., even when an image can be seen to be located directly in front of a user, the user""s eyes are focused on a more remote position).
Images viewed from many different angles of view can be recorded with ease by use of a micro lens array; however, when the thus-recorded images are reproduced in a reverse sequence, a user sees, from the back side, an image to be viewed from the front side (for example, when an image of a face is reproduced, the face can be seen, but the nose can been seen as being depressed). Therefore, integral photography has many drawbacks, including great labor such as cumbersome operation of reversing the image.
Meanwhile, stereoscope-type devices are often used at an exposition or a like place, and a user can enjoy stereoscopic images to some degree; however, such a stereoscope-type device, when considered as a no-glass-type device, has many imperfect portions. In addition, since pseudo-reproduction is effected after all, the stereoscopic images lack realism. Moreover, like integral photography, the stereoscope-type devices have a drawback in that a focus position does not coincide with a position of a viewed image.
As described above, no 3D image recording/reproduction device or system which is sufficiently practical exists at present, and therefore, proposal of a practical 3D image recording/reproduction device or system has been pursued.
Recording and reproduction of 3D images, in particular, motion pictures, which are the most important image information medium, are useful in many fields related to information, broadcasting, movies, and entertainment, and will become a large industry in future. Therefore, research on the recording and reproduction of 3D images has been carried out in many companies, universities, private research institutes, and public research institutes, both in Japan and overseas. However, no satisfactory device has yet been developed.
In order to break with the status quo, the present inventor has proposed a xe2x80x9clight ray reproduction methodxe2x80x9d in which a group of images of multiple viewpoints is projected by use of an array of point light sources in order to artificially generate a group of light rays corresponding to light scattered from an object, to thereby generate a 3D image (Japanese Patent Application Laid-Open (kokai) No. 10-239785). Moreover, the present inventor has proposed a xe2x80x9cthree-dimensional image reproduction device using a filterxe2x80x9d which has improved resolution (Japanese Patent Application Laid-Open (kokai) No. 11-232178). The proposed method and device resemble integral photography (hereinafter referred to as xe2x80x9cIPxe2x80x9d) in the point that a group of images of multiple viewpoints is used. However, the proposed method and device differ from IP in that the proposed method and device reproduce 3D images having depth and do not utilize parallax, or are rather similar to holography (when an image is photographed by use of a camera, the image is blurred except for the focused portion). The proposed method and device have succeeded in generating mostly satisfactory 3D images of simple objects.
Next, a technique which serves as the basis of the present invention will be described in detail.
FIG. 2 is a schematic view showing the principle of three-dimensional vision.
In FIG. 2, two points P and Q represent objects to be observed, and differ from each other in direction and distance. An observer 101 can detect the directions of the objects from the direction of light rays traveling toward the observer 101 and their distances from the parallax angles of the respective eyes through which the observer 101 views the point objects. Although FIG. 2 shows a finite number of light rays, in actuality, an infinite number of light rays are present. If such light rays can be generated, the observer 101 can view the two points three-dimensionally, even when the two points P and Q are not actually present.
In the above-described light ray reproduction method, such light rays are generated artificially in order to enable observation of a three-dimensional image. FIG. 3 shows a basic structure of a device used in the light ray reproduction method.
In FIG. 3, reference numeral 101 denotes an observer; 102 denotes an array of white-color point light sources; 103 denotes an image filter (for generation of light rays) on which images of multiple viewpoints are recorded; and 104 denotes a lens.
Since reproduction of an infinite number of light rays is impossible, as shown in FIG. 3, only light rays which pass through the white-color point light source array 102 distributed two-dimensionally are reproduced. Transmission (passage) points corresponding to point light sources of the white-color point light source array 102 are provided on the image filter 103, which is disposed to face the white-color point light source array 102; and the transmission (passage) points each have a color filter function for selecting a specific color from light emitted from the corresponding white-color point light source. In such a case, there can be reproduced colored light rays, each traveling along a straight line connecting a point light source and a corresponding passage point. When these light rays are focused on a single point Pxe2x80x2 by means of the lens 104, the light rays are observed by the observer 101 as if they were emitted from the point Pxe2x80x2, so that the point Pxe2x80x2 can be seen three-dimensionally.
A three-dimensional object is a set of points. Therefore, when proper transmission images of multiple viewpoints rather than dots are recorded on the image filter 103, the above-described configuration enables reproduction of a three-dimensional object.
Moreover, when a lens 104xe2x80x2 and another point object P are assumed as indicated by a dotted line in FIG. 3, the light rays passing through Pxe2x80x2 can be considered reproduction of light rays emitted from P. The observer can be considered to view the object Pxe2x80x2, or the observer can be considered to view a real image of the object P via the lenses 104xe2x80x2 and 104.
FIG. 4 shows an example of 3D object reproduction rather than point reproduction.
In FIG. 4, reference numeral 111 denotes a white-color light source; 112 denotes a pin-hole array; 113 denotes a color filter; 114 denotes a lens; 115 denotes an object to be observed; and 116 denotes an observer.
In FIG. 4, the function of the point light source array is realized through combined use of the white-color light source 111, a scatter plate (such as frosted glass), and the pin-hole array 112.
Here, the case in which the object 115 is present in front of the observer 116 will be considered. When light rays emitted from the point light sources of the array 102 shown in FIG. 3 or passed through the pin-holes of the pin-hole array 112 shown in FIG. 4 are passed through the color filter 113 for light ray reproduction and focused on the object 115 by means of the lens 114, the observer 116 observes the light rays as if they were emitted from the object 115. As a result, the object 115 can be seen three-dimensionally. In the case where the observer views an image generated by means of the lens 104 as shown in FIG. 3, two-dimensional images obtained upon observation of the object 115 from a specific point light source are recorded on a portion of the filter that faces the specific point light source, which is basically the same as recorded images in the case of integral photography (however, unlike the case of integral photography, images are not reversed in the course of reproduction).
In this case, when a micro lens is disposed at the point light source section or the pin-hole section and an actual object is photographed so as to form a positive image on the surface of a filter, the filter becomes a color filter. If resolution is not important, the pin-hole section is used as is in order to record pin-hole photographs, whereby loci of light rays are recorded as they are. In the case of CG or animation, images to be recorded are calculated and depicted by means of a computer without actual photographing.
The present inventor has succeeded in generating a color three-dimensional image by the above-described scheme.
However, the light ray reproduction method involves a big problem, in that the backstage such as a white-color point light source section and a filter section are exposed, leading to lack of realism.
The biggest problem involved in the above-described conventional devices is that not only a three-dimensional image generated upon reproduction of light rays, but also the backstage such as a filter and a white-color point light source array (pin-hole array) can be seen, because the depth of field of the human eye is deep, and scattering occurs at the filter section.
This may deteriorate the realism of a reproduced three-dimensional image. In addition, the conventional devices have a problem in that a group of light rays from the white-color point light source array or the pin-hole array cannot reproduce an image at the periphery of the filter section located in the vicinity thereof.
In the case of the conventional techniques, when a device is viewed from an observer side, not only a reproduced three-dimensional image, but also a white-color point light source array and a filter; i.e., the backstage, can be seen, thereby greatly deteriorating image quality.
The present inventor has attempted to use as a background a large portion of a filter (excepting for a portion for generating light rays for reproduction of a three-dimensional image); i.e., the backstage, in order to cover unnecessary scattered light by means of the background. An object of the present invention is to provide a device for reproducing a three-dimensional image with a background, which device can reproduce a very bright background image consisting of a large number of pixels and having a wide view angle, as well as a three-dimensional image standing out from the background or a three-dimensional image located behind the background image, at high S/N ratio, and which enables realization of so-called standing-out displays, standing-out signboards, and wall-mounted show windows.
In order to achieve the above object, the present invention provides the following.
[1] A device for reproducing a three-dimensional image with a background, characterized by comprising a white-color point light source array and a color transmission spatial distribution filter having a function of specially weighting intensity and color of light, wherein a group of light rays which can be seen as if the light rays were color light rays scattered from a three-dimensional color object is produced by use of light from the white-color point light source array and the color transmission spatial distribution filter; and color and/or intensity weights are imparted to the color transmission spatial distribution filter, except for a transmission portion used for reproduction of light rays of a three-dimensional object in such a manner that an image serving as a background of the three-dimensional object can be seen at the vicinity of the white-color point light source array or the filter.
[2] A device for reproducing a three-dimensional image with a background described in [1] above, characterized in that a single or a plurality of lenses are disposed between the color transmission spatial distribution filter and an observer.
[3] A device for reproducing a three-dimensional image with a background described in [1] or [2] above, characterized in that a white-color light source, a white-color scatter plate, and a pin-hole array are used in combination in place of the white-color point light source array.
As described in the above, the feature of the present invention resides in that a background image is provided on the filter and that the spatial filter has a portion which permits transmission of light (i.e., a portion to be used for reproduction of a three-dimensional image) and a portion which prevents transmission of light (i.e., a portion not to be used for reproduction of a three-dimensional image). This unused portion is colored and used as a background. From the viewpoint of overall configuration, the three-dimensional image reproduction device of the present invention consists of a white-color point light source array (or a pin-hole array, etc.) and a color transmission spatial distribution filter having a function of specially weighting intensity and color of light.